. . . . . . . . . . . . . . . . . "Directed graph"@en . . . . . . . . . "In mathematics, and more specifically in graph theory, a directed graph (or digraph) is a graph that is made up of a set of vertices connected by directed edges often called arcs."@en . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "15607"^^ . . "In mathematics, and more specifically in graph theory, a directed graph (or digraph) is a graph that is made up of a set of vertices connected by directed edges often called arcs."@en . . . "19721986"^^ . . . . . . "1052117995"^^ . . . . . . . . . . . . . . . . . . . . . . . . . . . .